In conventional paints containing dispersed pigments, depending on the nature of the pigment, poor dispersion stability can lead to pigment flocculation, or separation between the pigment and the binder resin (hereafter referred to as “Varnish separation”). One known method for resolving these problems involves the addition of a pigment dispersing agent to the paint. However, although pigment dispersing agents improve the dispersibility of the pigment, they tend to lower the weather resistance and heat resistance of the paint film, and if the pigment dispersing agent is colored, then achieving the desired paint hue can also be difficult.
Furthermore, in the case of a paint with an intermediate color, such as a paint with an intermediate color between red and yellow, pigments of different structural formulas, such as a red colored diketopyrrolopyrrole based pigment, quinacridone based pigment, or diaminoanthraquinone based pigment, and a yellow colored azo based pigment, isoindoline based pigment, or isoindolinone based pigment must be blended together.
Paints containing a plurality of pigments with different structural formulas tend to be more prone to pigment flocculation and varnish separation than paints that contain only one pigment. In order to prevent such pigment flocculation, a pigment dispersing agent must be added to the paint. The most suitable pigment dispersing agent will often differ for pigments with different structural formulas, meaning that in an intermediate colored paint containing a plurality of pigments with different structural formulas, a plurality of pigment dispersing agents are used. However, the most suitable pigment dispersing agent for one pigment may adversely affect the dispersibility of another pigment within the paint, thereby causing flocculation and a deterioration in the dispersion stability. Accordingly, in those cases where a plurality of pigment dispersing agents are combined, considerable care must be taken with the actual combination used.
Methods of generating an intermediate colored paint that involve the blending of pigments with similar structural formulas but a plurality of different hues also exist. Examples of pigments with similar structural formulas but a plurality of different hues include the benzimidazolone based compounds represented by a formula (2) (hereafter referred to as the “compound (2)”) and a formula (3) (hereafter referred to as the “compound (3)”) shown below (see W. Herbst and K. Hunger, “Industrial Organic Pigments, second completely revised edition” VCH Verlagsgesellschaft mbH, 1997, pp. 345 to 370).

These benzimidazolone based compounds are known to form a red to brown colored pigment when the molecular structure includes a naphthalene ring (the compound (2) shown above is red), and a yellow to orange colored pigment when the molecular structure does nor contain a naphthalene ring (the compound (3) shown above is yellow).
However, even in a paint prepared by blending the structurally similar compounds (2) and (3), the pigments still tend to flocculate, making it difficult to achieve the desired hue.